The predominantly hydrophobic nature of the trimerization of glucagon has been demonstrated by measurements of the temperature and concentration dependence of its circular dichroism. Fluorescence and CD studies of the effects of Hofmeister salts and hydrophogic probes were used to further characterize the hydrophobic nature of the trimerization of glucagon. Similar studies have been conducted on the cell surface protein isolated from fibroblasts by Yamada and Pastan. The protein appears to be very unstable and readily forms fibers, gels and films. The purified protein contains a mixture of monomer approximately 2 x 10 to the 5th power daltons) and dimer molecules. We have begun a study on the effect of various gangliosides on the binding of TSH to its solubilized receptor. Measurements of the critical micelle concentrations of gangliosides are underway. BIBLIOGRAPHIC REFERENCES: Edelhoch, H.: Structure of Polypeptide Hormones. In Chen, R.F. and Edelhoch, H. (Eds.): Biochemical Fluorescence Concepts. New York, Marcel Dekker, Inc., 1976, pp. 545-571. Frenoy, J.-P., Bourrillon, R., Lippoldt, R. and Edelhoch, H.: Stability and subunit structure of human alpha 2-marcoglobulin. J. Biol. Chem. 252: 1129-1133, 1977.